What about them asking what a lesbian is and one of the answers they get is two ponies of the same gender that love each other very much and they think that they're all lesbians for each other and say "Cutie Mark Crusaders Lesbians Forever!"?

Is see the adult ponies as adults, who do adult things out of the camera's eye. But, just like real life, those adult things have a tenancy of working their way into public life, if only through inference and rumor.